This invention relates to a device for sensing the torque developed during operation of a rotary drive system. The invention can be employed in various drive systems, e.g., automotive engine-transmission power plants, electric motor-operated tools, and metal cutting machines. In such drive systems, the torque-sensing feature may be useful for actuation of various control devices, such as electric switches, mechanical clutches, brake actuators, fluid control valves, or audible alarms. The torque-sensing function can be used for safety overload relief, motor de-energization, engine fuel control, transmission clutch actuation, remote alarm signal, tool breakage signal, etc.
Torque responsive systems are already known. For example, U.S. Pat. No. 1,953,182 to Lyon discloses an overload release mechanism wherein torque overloads mechanically disconnect the driven member from the drive member. In the Lyon patented arrangement, three radially oriented rollers are arranged so that during normal operations, each roller extends partly into a groove in the drive member and partly into a groove in the driven member; a spring urges the rollers more deeply into the grooves. Under overload conditions, the driven member tends to lag behind the drive member; at some overload point, the driven member exerts sufficient retarding force on the rollers to cause them to cam out of the driven member grooves against the spring force, thereby interrupting the driving connection between the drive and driven members.
U.S. Pat. No. 4,050,328 to R. Romick discloses a drive system that includes a drive shaft 66 having friction disk means disposed thereon within a driven member 68; spring means 146 urges the disk means to a drive-transmitting position. When an overload condition occurs, the spring means is unable to handle the overload force; the disk means then tends to spin within the driven member.
These patentend arrangements contemplate that when the torque setting is reached, the driven member will be mechanically spearated from the drive member. My contemplated apparatus differs from the patented arrangements in that no mechanical disconnection of the drive and driven members takes place when the torque setting is reached; the apparatus continues to transmit the drive force. The useful output of the torque-sensing apparatus is an electrical signal representative of the sensed torque condition. The apparatus has special usefulness where it is desired to keep the driven member operating when/after the torque setting is reached. The electric signal (representative of the sensed torque) can be used to operate or control various devices, such as alarms, fluid valves, motors, or clutches.